Lenticular laser incision for low myopia and/or hyperopia patients

ABSTRACT

Embodiments generally relate to ophthalmic laser procedures and, more particularly, to systems and methods for lenticular laser incisions to form a top lenticular incision, a bottom lenticular incision of a lens in the subject&#39;s eye, an added shape between the top and bottom incisions where the added shape has no corrective power and a transition ring bisecting both the top and bottom lenticular incisions.

RELATED APPLICATIONS

This application claims priority to, and the benefit of, under 35 U.S.C.§ 119(e) of U.S. Provisional Appl. No. 62/356,430, filed Jun. 29, 2016,which is incorporated herein by reference in its entirety.

FIELD

Embodiments of this invention relate generally to laser-assistedophthalmic procedures, and more particularly, to systems and methods forlenticular incisions in the cornea for low myopia and/or hyperopiapatients.

BACKGROUND

Vision impairments such as myopia (near-sightedness), hyperopia(far-sightedness) and astigmatism can be corrected using eyeglasses orcontact lenses. Alternatively, the cornea of the eye can be reshapedsurgically to provide the needed optical correction. Eye surgery hasbecome commonplace with some patients pursuing it as an electiveprocedure to avoid using contact lenses or glasses to correct refractiveproblems, and others pursuing it to correct adverse conditions such ascataracts. And, with recent developments in laser technology, lasersurgery is becoming the technique of choice for ophthalmic procedures.The reason eye surgeons prefer a surgical laser beam over manual toolslike microkeratomes and forceps is that the laser beam can be focusedprecisely on extremely small amounts of ocular tissue, thereby enhancingaccuracy and reliability of the procedure. These in turn enable betterwound healing and recovery following surgery.

Hyperopia (far-sightedness) is a visual impairment where light enteringthe eye does not focus at the retina to produce a sharp image asdesired, but rather focuses at a location behind the retina such that apatient sees a blurred disc. The basic principle to treating hyperopiais to add positive focusing power to the cornea. For instance, ahyperopic eye can be treated by placing a convex lens in front of theeye to add a positive focusing power to the eye. After correction, lightpassing through the convex lens and into the eye focuses at the retinato form a sharp image.

Different laser eye surgical systems use different types of laser beamsfor the various procedures and indications. These include, for instance,ultraviolet lasers, infrared lasers, and near-infrared, ultra-shortpulsed lasers. Ultra-short pulsed lasers emit radiation with pulsedurations as short as 10 femtoseconds and as long as 3 nanoseconds, anda wavelength between 300 nm and 3000 nm. Examples of laser systems thatprovide ultra-short pulsed laser beams include the Abbott Medical OpticsiFS Advanced Femtosecond Laser, the IntraLase FS Laser, and theOptiMedica Catalys Precision Laser System.

Prior surgical approaches for reshaping the cornea include laserassisted in situ keratomileusis (hereinafter “LASIK”), photorefractivekeratectomy (hereinafter “PRK”) and Small Incision Lens Extraction(hereinafter “SMILE”).

In the LASIK procedure, an ultra-short pulsed laser is used to cut acorneal flap to expose the corneal stroma for photoablation withultraviolet beams from an excimer laser. Photoablation of the cornealstroma reshapes the cornea and corrects the refractive condition such asmyopia, hyperopia, astigmatism, and the like.

If part of the cornea is removed, the pressure exerted on the cornea bythe aqueous humor in the anterior chamber of the eye will act to closethe void created in the cornea, resulting in a reshaped cornea. Byproperly selecting the size, shape and location of a corneal void, onecan obtain the desired shape, and hence, the desired optical propertiesof the cornea.

In traditional laser surgery treatments, such as LASIK and PRK thatcorrect hyperopia, positive focusing power is added to the cornea bysteepening the curvature of the cornea, by for example, removing aring-shaped stroma material from the cornea. As described earlier, in aLASIK procedure, first, a flap is created, and then, it is lifted so thering-shaped stroma material can be removed or ablated with an excimerlaser. The center of the cornea is not removed while more outwardportions of the cornea are removed. The flap is then put back intoplace. The cornea thus steepens due to the void created in the cornea.Common patterns that steepen the cornea include ring, tunnel and toricshapes. LASIK can typically correct hyperopia for up to 5D (diopter). Ina PRK procedure where no flap is created, the epithelium layer is firstremoved, and the ring-shaped stroma material is then removed by anexcimer laser. The epithelium layer will grow back within a few daysafter the procedure.

More recently, surgeons have started using another surgical techniqueother than LASIK and PRK for refractive correction. Instead of ablatingcorneal tissue with an excimer laser following the creation of a cornealflap, the newer SMILE technique involves tissue removal with twofemtosecond laser incisions that intersect to create a lenticule forextraction. Lenticular extractions can be performed either with orwithout the creation of a corneal flap. With the flapless procedure, arefractive lenticule is created in the intact portion of the anteriorcornea and removed through a small incision. But, patients with lowmyopia and/or hyperopia can end up with a relatively small lenticule,which can be difficult to extract.

SUMMARY

Hence, to obviate one or more problems due to limitations anddisadvantages of the related art, this disclosure provides improvedsystems and methods for generating corneal lenticular incisions forcorrecting low myopia and/or hyperopia using high repetition ratefemtosecond lasers. Embodiments of this invention including anophthalmic surgical laser system comprising a laser delivery system fordelivering a pulsed laser beam to a target in a subject's eye, anXY-scan device to deflect the pulsed laser beam, a Z-scan device tomodify a depth of a focus of the pulsed laser beam, and a controllerconfigured to form a top lenticular incision and a bottom lenticularincision of a lens on the subject's eye. The XY-scan device deflects thepulsed laser beam to form a scan line. The scan line is tangential tothe parallels of latitude of the lens. The scan line is then moved alongthe meridians of longitude of the lens. The top lenticular incision ismoved over the top surface of the lens through the apex of the topsurface of the lens, and the bottom lenticular incision is moved overthe bottom surface of the lens through the apex of bottom surface of thelens.

Other embodiments disclose an ophthalmic surgical laser systemcomprising a laser delivery system for delivering a pulsed laser beam toa target in a subject's eye, an XY-scan device to deflect the pulsedlaser beam, a Z-scan device to modify a depth of a focus of the pulsedlaser beam, and a controller configured to form a top concave lenticularincision, a bottom concave lenticular incision, and a transition ringincision intersecting both the top and bottom lenticular incisionsforming a lens on the subject's corneal stroma.

This summary and the following detailed description are merelyexemplary, illustrative, and explanatory, and are not intended to limit,but to provide further explanation of the embodiments as claimed.Additional features and advantages of the embodiments will be set forthin the descriptions that follow, and in part will be apparent from thedescription, or may be learned by practice of the embodiments. Theobjectives and other advantages of the embodiments will be realized andattained by the structure particularly pointed out in the writtendescription, claims and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the embodiments are set forth with particularityin the appended claims. A better understanding of the features andadvantages will be facilitated by referring to the following detaileddescription that sets forth illustrative embodiments, as well as to theaccompanying drawings, in which like numerals refer to like partsthroughout the different views. Like parts, however, do not always havelike reference numerals. Further, the drawings are not drawn to scale,and emphasis has instead been placed on illustrating the principles ofthe embodiments. All illustrations are intended to convey concepts,where relative sizes, shapes, and other detailed attributes may beillustrated schematically rather than depicted literally or precisely.

FIG. 1 illustrates a conventional lenticular cut via scanning a singlefocus spot according to certain embodiments.

FIG. 2 is a simplified diagram of a surgical ophthalmic laser systemaccording to certain embodiments.

FIG. 3 is another simplified diagram of a surgical ophthalmic lasersystem according to certain embodiments.

FIG. 4 is a simplified diagram of a controller of a surgical ophthalmiclaser system according to certain embodiments.

FIG. 5 illustrates an exemplary scanning of a surgical ophthalmic lasersystem according to certain embodiments.

FIG. 6 illustrates an exemplary lenticular incision using afast-scan-slow-sweep scheme of a surgical ophthalmic laser systemaccording to certain embodiments.

FIG. 7 illustrates a geometric relation between a fast scan line and anintended spherical dissection surface of a surgical ophthalmic lasersystem according to certain embodiments.

FIG. 8 illustrates an exemplary lenticular incision using a surgicalophthalmic laser system according to certain embodiments.

FIG. 9 is a flowchart illustrating a process according to certainembodiments.

FIG. 10 illustrates an exemplary Small Incision Lenticule Extractionprocedure according to certain embodiments.

FIG. 11A illustrates an exemplary side view of two lenticular incisionsaccording to certain embodiments.

FIG. 11B illustrates an exemplary side view of two lenticular incisionsand a transition ring according to certain embodiments.

FIG. 12 is a flowchart illustrating an exemplary surgery processaccording to certain embodiments.

FIG. 13 illustrates an exemplary perspective view of cuts used to formand extract lenticular tissue according to certain embodiments.

FIG. 14 illustrates an exemplary perspective view of cuts used to formand extract lenticular tissue with a transition ring according tocertain embodiments.

FIG. 15 illustrates exemplary views of corneas and lenticules accordingto certain embodiments.

FIG. 16 illustrates exemplary diagrams of calculations of addedlenticule thickness according to certain embodiments.

DETAILED DESCRIPTION

Embodiments are generally directed to systems and methods forlaser-assisted ophthalmic procedures, and more particularly, to systemsand methods for lenticular laser incisions for patients with low myopiaand/or hyperopia.

Referring to the drawings, FIG. 2 shows a system 10 for making anincision in a material 12. The system 10 includes, but is not limitedto, a laser 14 capable of generating a pulsed laser beam 18, an energycontrol module 16 for varying the pulse energy of the pulsed laser beam18, a Z-scanner 20 for modifying the depth of the pulse laser beam 18, acontroller 22, a prism 23 (e.g., a Dove or Pechan prism, or the like),and an XY-scanner 28 for deflecting or directing the pulsed laser beam18 from the laser 14 on or within the material 12. The controller 22,such as a processor operating suitable control software, is operativelycoupled with the Z-scanner 20, the XY-scanner 28, and the energy controlunit 16 to direct a scan line 30 of the pulsed laser beam along a scanpattern on or in the material 12. In this embodiment, the system 10further includes a beam splitter 26 and a detector 24 coupled to thecontroller 22 for a feedback control mechanism (not shown) of the pulsedlaser beam 18. Other feedback methods may also be used, including butnot necessarily limited to position encoder on the scanner 20, or thelike. In an embodiment, the pattern of pulses may be summarized inmachine readable data of tangible storage media in the form of atreatment table. The treatment table may be adjusted according tofeedback input into the controller 22 from an automated image analysissystem in response to feedback data provided from an ablation monitoringsystem feedback system (not shown). Optionally, the feedback may bemanually entered into the controller 22 by a system operator. Thefeedback may also be provided by integrating a wavefront measurementsystem (not shown) with the laser surgery system 10. The controller 22may continue and/or terminate a sculpting or incision in response to thefeedback, and may also modify the planned sculpting or incision based atleast in part on the feedback. Measurement and imaging systems arefurther described in U.S. Pat. Nos. 6,315,413 and 8,260,024, thecomplete disclosures of which are incorporated herein by reference.

In an embodiment, the system 10 uses a pair of scanning mirrors or otheroptics (not shown) to angularly deflect and scan the pulsed laser beam18. For example, scanning mirrors driven by galvanometers may beemployed where each of the mirrors scans the pulsed laser beam 18 alongone of two orthogonal axes. A focusing objective (not shown), whetherone lens or several lenses, images the pulsed laser beam 18 onto a focalplane of the system 10. The focal point of the pulsed laser beam 18 maythus be scanned in two dimensions (e.g., the x-axis and the y-axis)within the focal plane of the system 10. Scanning along the thirddimension, e.g., moving the focal plane along an optical axis (e.g., thez-axis), may be achieved by moving the focusing objective, or one ormore lenses within the focusing objective, along the optical axis.

Laser 14 may comprise a femtosecond laser capable of providing pulsedlaser beams, which may be used in optical procedures, such as localizedphotodisruption (e.g., laser induced optical breakdown). Localizedphotodisruptions can be placed at or below the surface of the materialto produce high-precision material processing. For example, amicro-optics scanning system may be used to scan the pulsed laser beamto produce an incision in the material, create a flap of the material,create a pocket within the material, form removable structures of thematerial, and the like. The term “scan” or “scanning” refers to themovement of the focal point of the pulsed laser beam along a desiredpath or in a desired pattern.

In other embodiments, the laser 14 may comprise a laser sourceconfigured to deliver an ultraviolet laser beam comprising a pluralityof ultraviolet laser pulses capable of photo decomposing one or moreintraocular targets within the eye.

Although the laser system 10 may be used to photo alter a variety ofmaterials (e.g., organic, inorganic, or a combination thereof), thelaser system 10 is suitable for ophthalmic applications in certainembodiments. In these cases, the focusing optics direct the pulsed laserbeam 18 toward an eye (for example, onto or into a cornea) for plasmamediated (for example, non-UV) photo ablation of superficial tissue, orinto the stroma of the cornea for intrastromal photo disruption oftissue. In these embodiments, the surgical laser system 10 may alsoinclude a lens to change the shape (for example, flatten or curve) ofthe cornea prior to scanning the pulsed laser beam 18 toward the eye.

The laser system 10 is capable of generating the pulsed laser beam 18with physical characteristics similar to those of the laser beamsgenerated by a laser system disclosed in U.S. Pat. Nos. 4,764,930,5,993,438, and U.S. patent application Ser. No. 12/987,069, filed Jan.7, 2011, which are incorporated herein by reference.

FIG. 3 shows another exemplary diagram of the laser system 10. FIG. 3shows a moveable XY-scanner (or XY-stage) 28 of a miniaturizedfemtosecond laser system. In this embodiment, the system 10 uses afemtosecond oscillator, or a fiber oscillator-based low energy laser.This allows the laser to be made much smaller. The laser-tissueinteraction is in the low-density-plasma mode. An exemplary set of laserparameters for such lasers include pulse energy in the 50-100 nJ rangeand pulse repetitive rates (or “rep rates”) in the 5-20 MHz range. Afast-Z scanner 20 and a resonant scanner 21 direct the laser beam 18 tothe prism 23. When used in an ophthalmic procedure, the system 10 alsoincludes a patient interface 31 design that has a fixed cone nose and aportion that engages with the patient's eye. A beam splitter is placedinside the cone of the patient interface to allow the whole eye to beimaged via visualization optics. In one embodiment, the system 10 uses:optics with a 0.6 numerical aperture (NA) which would produce 1.1 μmFull Width at Half Maximum (FWHM) focus spot size; and a resonantscanner 21 that produces 1-2 mm scan line with the XY-scanner scanningthe resonant scan line to a 10 mm field. The prism 23 rotates theresonant scan line in any direction on the XY plane. The fast-Z scanner20 sets the incision depth and produces a side cut. The system 10 mayalso include an auto-Z module 32 to provide depth reference. Theminiaturized femtosecond laser system 10 may be a desktop system so thatthe patient sits upright while being under treatment. This eliminatesthe need of certain opto-mechanical arm mechanism(s), and may reduce thecomplexity, size, and weight of the laser system. Alternatively, theminiaturized laser system may be designed as a conventional femtosecondlaser system, where the patient is treated while lying down.

FIG. 4 illustrates a simplified block diagram of an exemplary controller22 that may be used by the laser system 10 according to someembodiments. Controller 22 may include at least one processor 52 whichmay communicate with a number of peripheral devices via a bus subsystem54. These peripheral devices may include a storage subsystem 56,including a memory subsystem 58 and a file storage subsystem 60, userinterface input devices 62, user interface output devices 64, and anetwork interface subsystem 66. Network interface subsystem 66 providesan interface to outside networks 68 and/or other devices. Networkinterface subsystem 66 includes one or more interfaces known in thearts, such as LAN, WLAN, Bluetooth, other wire and wireless interfaces,and so on.

User interface input devices 62 may include a keyboard, pointing devicessuch as a mouse, trackball, touch pad, or graphics tablet, a scanner,foot pedals, a joystick, a touch screen incorporated into a display,audio input devices such as voice recognition systems, microphones, andother types of input devices. In general, the term “input device” isintended to include a variety of conventional and proprietary devicesand ways to input information into controller 22.

User interface output devices 64 may include a display subsystem, aprinter, a fax machine, or non-visual displays such as audio outputdevices. The display subsystem may be a flat-panel device such as aliquid crystal display (LCD), a light emitting diode (LED) display, atouchscreen display, or the like. The display subsystem may also providea non-visual display such as via audio output devices. In general, theterm “output device” is intended to include a variety of conventionaland proprietary devices and ways to output information from controller22 to a user.

Storage subsystem 56 can store the basic programming and data constructsthat provide the functionality of the various embodiments. For example,a database and modules implementing the functionality of the methods ofthe present embodiments, as described herein, may be stored in storagesubsystem 56. These software modules are generally executed by processor52. In a distributed environment, the software modules may be stored ona plurality of computer systems and executed by processors of theplurality of computer systems. Storage subsystem 56 typically comprisesmemory subsystem 58 and file storage subsystem 60.

Memory subsystem 58 typically includes a number of memories including amain random access memory (RAM) 70 for storage of instructions and dataduring program execution and a read only memory (ROM) 72 in which fixedinstructions are stored. File storage subsystem 60 provides persistent(non-volatile) storage for program and data files. File storagesubsystem 60 may include a hard disk drive along with associatedremovable media, a Compact Disk (CD) drive, an optical drive, DVD,solid-state memory, and/or other removable media. One or more of thedrives may be located at remote locations on other connected computersat other sites coupled to controller 22. The modules implementing thefunctionality of the present embodiments may be stored by file storagesubsystem 60.

Bus subsystem 54 provides a mechanism for letting the various componentsand subsystems of controller 22 communicate with each other as intended.The various subsystems and components of controller 22 need not be atthe same physical location but may be distributed at various locationswithin a distributed network. Although bus subsystem 54 is shownschematically as a single bus, alternate embodiments of the bussubsystem may utilize multiple busses.

Due to the ever-changing nature of computers and networks, thedescription of controller 22 depicted in FIG. 4 is intended only as anexample for purposes of illustrating only some embodiments. Many otherconfigurations of controller 22, having more or fewer components thanthose depicted in FIG. 4, are possible.

As should be understood by those of skill in the art, additionalcomponents and subsystems may be included with laser system 10. Forexample, spatial and/or temporal integrators may be included to controlthe distribution of energy within the laser beam, as described in U.S.Pat. No. 5,646,791, which is incorporated herein by reference. Ablationeffluent evacuators/filters, aspirators, and other ancillary componentsof the surgical laser system are known in the art, and may be includedin the system. In addition, an imaging device or system may be used toguide the laser beam. Further details of suitable components ofsubsystems that can be incorporated into an ophthalmic laser system forperforming the procedures described here can be found incommonly-assigned U.S. Pat. Nos. 4,665,913, 4,669,466, 4,732,148,4,770,172, 4,773,414, 5,207,668, 5,108,388, 5,219,343, 5,646,791,5,163,934, 8,394,084, 8,403,921, 8,690,862, 8,709,001, U.S. patentapplication Ser. No. 12/987,069, filed Jan. 7, 2011 (published asUS20110172649), U.S. patent application Ser. No. 13/798,457 filed Mar.13, 2013 (published as US20140104576), U.S. patent application Ser. No.14/848,733, filed Sep. 9, 2015, U.S. patent application Ser. No.14/865,396, filed Sep. 25, 2015, U.S. patent application Ser. No.14/968,549, filed Dec. 14, 2015, and U.S. patent application Ser. No.14/970,898, filed Dec. 16, 2015, which are incorporated herein byreference.

In an embodiment, the laser surgery system 10 includes a femtosecondoscillator-based laser operating in the MHz range, for example, 10 MHz,for example, from several MHz to tens of MHz. For ophthalmicapplications, the XY-scanner 28 may utilize a pair of scanning mirrorsor other optics (not shown) to angularly deflect and scan the pulsedlaser beam 18. For example, scanning mirrors driven by galvanometers maybe employed, each scanning the pulsed laser beam 18 along one of twoorthogonal axes. A focusing objective (not shown), whether one lens orseveral lenses, images the pulsed laser beam onto a focal plane of thelaser surgery system 10. The focal point of the pulsed laser beam 18 maythus be scanned in two dimensions (e.g., the X-axis and the Y-axis)within the focal plane of the laser surgery system 10. Scanning along athird dimension, e.g., moving the focal plane along an optical axis(e.g., the Z-axis), may be achieved by moving the focusing objective, orone or more lenses within the focusing objective, along the opticalaxis. It is noted that in many embodiments, the XY-scanner 28 deflectsthe pulse laser beam 18 to form a scan line.

In some embodiments, the beam scanning can be realized with a“fast-scan-slow-sweep” scanning scheme. The scheme consists of twoscanning mechanisms: first, a high frequency fast scanner is used toproduce a short, fast scan line (e.g., a resonant scanner 21 of FIG. 3);second, the fast scan line is slowly swept by much slower X, Y, and Zscan mechanisms. FIG. 5 illustrates a scanning example of a laser system10 using an 8 kHz resonant scanner 21 to produce a scan line of about 1mm and a scan speed of about 25 m/sec, and X, Y, and Z scan mechanismswith the scan speed smaller than 0.1 m/sec. The fast scan line may beperpendicular to the optical beam propagation direction, e.g., it isalways parallel to the XY plane. The trajectory of the slow sweep can beany three dimensional curve drawn by the X, Y, and Z scanning devices(e.g., XY-scanner 28 and Z-scanner 20). An advantage of the“fast-scan-slow-sweep” scanning scheme is that it only uses small fieldoptics (e.g., a field diameter of 1.5 mm) which can achieve high focusquality at relatively low cost. The large surgical field (e.g., a fielddiameter of 10 mm or greater) is achieved with the XY-scanner, which maybe unlimited.

In some embodiments, as shown for example in FIG. 6, the laser system 10creates a smooth lenticular cut using the “fast-scan-slow-sweep”scanning scheme under a preferred procedure. First, in a threedimensional lenticular cut, the fast scan line is preferably placedtangential to the parallels of latitude 610. For example, in theminiaturized flap maker laser system 10 of FIG. 3, this can be realizedby adjusting a prism 23 to the corresponding orientations via software,e.g., via the controller 22. Second, the slow sweep trajectorypreferably moves along the meridians of longitude 620. For example, inthe miniaturized flap maker system of FIG. 3, this can be done bycoordinating the XY scanner 28, and the Fast-Z scanner 20 via thesoftware, e.g., via the controller 22. The procedure starts with thescan line being parallel to the XY plane, and sweeps through the apex ofthe lens, following the curvature with the largest diameter (see alsoFIG. 8). With this preferred procedure, there are no vertical “steps” inthe dissection, and vertical side cuts are eliminated. As will beanalyzed herein below, the deviations between the laser focus locationsand the intended spherical surface dissections are also minimized.

FIG. 7 shows the geometric relation between the fast scan line 710 andthe intended spherical dissection surface 720, e.g., of a lens,especially the distance deviation (δ) between the end point B of thescan line 720 and point A on the intended dissection surface 720. Themaximum deviation δ is the distance between point A and point B, and isgiven by

${\delta = {{\sqrt{R^{2} + \frac{L^{2}}{4}} - R} = \frac{L^{2}}{8R}}},$equation (1), where R is greater than L. R is the radius of curvature ofthe surface dissection 720, and L is the length of the fast scan.

In an exemplary case of myopic correction, the radius of curvature ofthe surface dissection may be determined by the amount of correction,ΔD, using the following equation

${{\Delta\; D} = {\frac{( {n - 1} )}{R_{1}} + \frac{( {n - 1} )}{R_{2}}}},$equation (2), where n=1.376, which is the refractive index of cornea,and R₁ and R₂ (may also be referred herein as R_(t) and R_(b)) are theradii of curvature for the top surface and bottom surface of alenticular incision, respectively. For a lenticular incision withR₁=R₂=R (the two dissection surface are equal for them to physicallymatch and be in contact), we have

${R = \frac{2( {n - 1} )}{\Delta\; D}},$equation (3).

In an embodiment, FIG. 8 shows an exemplary lenticular incision 900 forextraction using the laser system 10. FIG. 8 shows an exemplarycross-sectional view 910 illustrating a patient interface 905 (orpatient interface 31 as shown in FIG. 3), cornea 906, and lenticularincision volume 915, which will be referred herein as lens to beextracted. Rt and Rb are the radii of curvature for the top surface andbottom surface of a lenticular incision, respectively. ZFt (Zt) is thedepth of the top surface of the lenticular incision. ZFb (Zb) is thedepth of the bottom surface of the lenticular incision. The Z depths maybe calculated based on the respective radii. LT is the lens thickness atthe lens apex, or center thickness of the lens. ZA is depth of the lensapex. DL is the diameter of the lenticular incision, or the lens.{Z_SLOW=0} is the Z reference position before the laser system 10calculates and sets Z_SLOW, e.g., {Z_SLOW=ZA+LT/2} the center depth ofthe lens, which remains fixed for the duration of the incisionprocedure. Z_SLOW may then be the reference position for the Z-scannerfor top and bottom incision surfaces. In an embodiment, the diameter ofthe lens may be received from an operator of the laser system 10, or maybe calculated by the laser system 10. The thickness of the lens may bedetermined, for example, by the total amount of correction (e.g.,diopter) and the diameter of the lens.

A top view 950 of the lenticular incision 900 illustrates threeexemplary sweeps (1A to 1B), (2A to 2B) and (3A to 3B), with each sweepgoing through (e.g., going over) the lenticular incision apex 955. Theincision, or cut, diameter 957 (D_(CUT)) should be equal to or greaterthan the to-be-extracted lenticular incision diameter 917 (DL). A topview 980 shows the top view of one exemplary sweep. In some embodiments,the lenticular incision may be performed in the following steps:

1. Calculate the radius of curvature based on the amount of correction,e.g., a myopic correction.

2. Select the diameter for the lenticular incision to be extracted.

3. Perform the side incision first (not shown) to provide a vent for gasthat can be produced in the lenticular surface dissections. This is alsothe incision for the entry of forceps and for lens extraction.

4. Perform bottom surface dissection (the lower dissection as shown incross-sectional view 910). In doing so, the fast scan line is preferablykept tangential to the parallels of latitude, and the trajectory of theslow sweep drawn by X, Y, and Z scanning devices moves along themeridians of longitude (near south pole in a sequence of 1A→1B (firstsweep of lenticular cut), 2A→2B (second sweep of lenticular cut), 3A→3B(third sweep of lenticular cut), and so on, until the full bottomdissection surface is generated.

5. Perform the top surface dissection (the upper dissection as shown inthe cross-sectional view 910) in a similar manner as the bottomdissection is done. It is noted that the bottom dissection is donefirst. Otherwise, the bubble generated during the top dissection willblock the laser beam in making the bottom dissection.

For illustrative purposes, in a myopic correction of ΔD=10 diopter(e.g., 1/m), using equation (3), R=75.2 mm, which is indeed much greaterthan the length L of the fast scan. Assuming a reasonable scan linelength of L=1 mm, using equation (1), the deviation δ≈1.7 μm. Thisdeviation is thus very small. For comparison purpose, the depth of focusof a one micron (FWHM) spot size at 1 μm wavelength is about ±3 μm,meaning the length of focus is greater than the deviation δ.

FIG. 9 illustrates a process 1000 of the laser system 10 according to anembodiment. The laser system 10 may start a surgical procedureperforming pre-operation measurements 1010. For example, in anophthalmologic surgery for myopic correction, the myopic diopter isdetermined, the SLOW_Z position is determined, and so on. The lasersystem 10 calculates the radius of curvature based on the amount ofcorrection, e.g., the myopic correction determined in pre-operationmeasurements (Action Block 1020), as shown, for example, in equations(2) and (3) above. The laser system 10 calculates the diameter of theincision 1030, as shown by D_(CUT) in FIG. 8. D_(CUT) is equal to orgreater than the diameter of the to-be-extracted lenticule (DL in FIG.8). The laser system 10 first performs side incision to provide a ventfor gas that can be produced in the lenticular surface dissections, andfor tissue extraction later on 1040. The laser system 10 then performsthe bottom lenticular surface dissection 1050 before performing the toplenticular surface dissection 1060. The lenticular tissue is thenextracted 1070.

In other embodiments, the laser system 10 may also be used to produceother three-dimensional surface shapes, including toric surfaces forcorrecting hyperopia and astigmatism. The laser system 10 may also beused for laser material processing and micromachining for othertransparent materials. Correction of hyperopia by the laser system 10 isdiscussed in detail below.

In the SMILE procedure illustrated in FIG. 10, a femtosecond laser 110is used to make a side cut 120, an upper or top surface cut 130 and alower or bottom surface cut 140 that forms a cut lens or lenticule 150.A tweezer, for example, may then be used to extract the cut lens beneaththe anterior surface of the cornea 160 through the side cut 120. SMILEmay be applied to treat myopia and/or hyperopia by cutting andextracting a convex lens-shaped stroma material with a femtosecondlaser. However, SMILE techniques have not been applied in treatinghyperopia.

Low Myopic/Hyperopic Correction Examples

In certain treatment examples, a patient may only need a minorrefractive correction for low-power myopia (e.g. −0.5 diopters (D) to−4.0 D) or low-power hyperopia (+2.0 D). The systems and methodsdescribed here using high reprate (MHz range) femtosecond lasers may beused to incise precise concave incisions within the corneal tissue andcreate a correction for the patient. But with minor corrections theconcave cuts may be shallow and the thickness of the resultinglenticular tissue small. And a small lenticule may be difficult toextract especially if the lenticular tissue is pulled through anextraction cut.

Systems and methods here may be used to widen the gap between the upperand lower lenticular cuts making the lenticular tissue for extractionthicker and easier to remove. In some examples, a 50 μm lenticulethickness may ease lenticule extraction. The systems and methods canachieve this while maintaining the refractive correction necessary forthe patient and also maintaining an appropriately sized diameter cut.

FIG. 11A shows a side view illustration of two example lenticularincisions in a cornea used to make the required power correction in theeye as described herein. In this example, the patient had a low myopiaand/or hyperopia correction.

Low myopia (or hyperopia) corrections may require a shallower curve tothe top and bottom lenticular incisions than incisions used to correct ahigh myopia (or hyperopia). Such shallowly angled incisions for the topand bottom surfaces of the lenticular incisions may result in a verythin lenticular tissue 1102 only 21 μm thick, in this example, withdifferent corrections resulting in different thicknesses.

Because the corneal stroma is curved and the eye is only so large, itmay be desirable to limit the diameter of any intrastromal incision toensure the integrity of the eye after treatment. For example, thediameter of the lenticule in FIG. 11A is between 5 and 9 mm, for example8.0 mm wide. As discussed above, in order to facilitate removal of thelenticular tissue between the top and bottom surface incisions, theincisions for the top and bottom lenticular surfaces may overlapslightly at the edges 1110. Such an overlap may help ensure that thereis no tissue bridging with the cornea and incised lenticule which is tobe extracted. And because extraction may be from any method including bypulling the incised lenticule out of an extraction cut with a forceps,it may be difficult pulling a thin lenticule out of the extraction cutwithout tearing the thin lenticular tissue.

FIG. 11B shows a side view illustration of two example lenticularincisions used in some embodiments described here, but this time, thetwo lenticular incisions are spaced wider apart and there is atransition ring 1120. Again, this example shows an 8.0 mm diameterlenticule but with the incisions spaced wider apart, here 65 μm as anexample. As the curved lenticular incisions affect the correction of theeye, and not the amount of corneal tissue removed, the overall thicknessof the lenticular tissue is irrelevant in terms of refractivecorrection. Thus, by spacing the two lenticular cuts apart, the samecorrection may be made with a resulting thicker lenticular tissue. Thisthicker tissue may be easier to extract.

It is clear that by incising the top and bottom lenticular incisionswith a wider space between them, the overall lenticular tissue wouldalso need to be larger in diameter 1142 if the curvature of theincisions remained constant. In the example of FIG. 11B, dashed linesshow where the two wider spaced lenticular incisions would overlap 1140if they continued at the same curvature angle as they did in the exampleof FIG. 11A. But in the example of FIG. 11B, the diameter of thelenticular tissue is the same as in FIG. 11A, 8.0 mm. Thus, to get thelenticular tissue diameter to remain at 8 mm, and thereby make the topand bottom incisions to overlap at 8 mm, a transition ring 1120 may becut. The transition ring 1120 may be cut to join the top and bottomincisions at a different curvature angle in order to change the diameter1142 of the lenticule had it otherwise not been incised.

By incising this transition ring around the circumference of thelenticular tissue, the same correction lenticular cuts may be made andthe same diameter of the lenticular tissue may be incised as describedin FIG. 11A, but the result would be a thicker lenticule that may beeasier to remove. Such a transition ring may encompass the lenticule andprovide >50 μm lenticule thickness along with the required separation ofthe lenticule from the cornea, and also a smooth transition fromlenticule top surface to bottom surface.

Such a transition ring 1120, with a steeper curvature angle, may alsoresult in a cleaner lenticule edge which may make extraction easier.Such relatively steeper cuts may result in less tissue bridging thanshallower cuts. It should be noted that the transition ring 1120 couldbe incised at any angle and form any diameter lenticule, so long as thetop and bottom lenticular incisions are made for the proper refractivecorrection and so long as the lenticule effectively covered the pupiland refracted the light entering the pupil. The transition ring 1120, asviewed from the side as shown in FIG. 11B, could be a straight incisionto join the top and bottom incisions, or it could be angled or curved asshown in FIG. 11B. Any kind of curvature may be incised by the lasers asdescribed above.

It should be noted that the transition ring 1120 may be incised, even incases where the top and bottom lenticular incisions do actually meet oreven overlap. A transition ring 1120 may be useful to clean up an edgeor make extraction easier, even in cases where the top and bottomincisions are not spaced farther apart. Because the transition ring canbe any depth and take any form of curvature, it can be tailored to theneeds of individual patients.

FIG. 12 is a flowchart illustrating an exemplary surgery process 1200according to some embodiments here. The laser system 10 may start asurgical procedure performing pre-operation measurements 1210. Forexample, in an ophthalmologic surgery for hyperopic correction, thehyperopic diopter is determined, the SLOW_Z position is determined, andso on. The laser system 10 calculates the shape of the incisions 1220.The laser system 10 calculates the radius of curvatures based on theamount of correction, e.g., the hyperopic correction determined inpre-operation measurements 1230, as determined by Equations (4)-(8), forexample. The laser system 10 first performs a side incision to provide avent for gas that can be produced in the lenticular surface dissections,and for tissue extraction later on 1240. The laser system 10 thenperforms the bottom lenticular surface dissection 1250 before performingthe top lenticular surface dissection 1260. Performing the dissectionsin this order allows gas to vent out of the cornea instead of becomingtrapped in gas bubbles within the cornea. This order also preventshaving to traverse the focal point of the laser beam through incisedtissue. It should be noted that in the embodiments described here, thesebottom surface 1250 and top surface 1260 would not necessarily meet ortouch. In other words, the edges of the top and bottom cuts may have aspace in between. Next, a transition ring cut is made around thecircumference of the lenticular tissue 1270. This transition ring,depending on the space between the edges of the top and bottomincisions, may then join the two incisions and create a lenticule. Thelenticular tissue may then be extracted from the side cut.

FIG. 13 shows an example perspective of a lenticular tissue after thetwo main incisions 1310, which are designed to make the required powercorrection in the eye. In the example, the cornea itself is not shown,but the outline of the lenticule 1310 and side cut 1320 only. The topand bottom cut surfaces may overlap to facilitate separation of thelenticule from the eye. In this example, the correction is low so theresulting lenticular tissue is thin, only a few μm. As discussed above,extracting a thin lenticular tissue may be difficult and may result incollateral damage and tearing. The other incision is the side extractionincision 1320.

FIG. 14 shows an example perspective of a lenticular tissue after thetwo main incisions 1410, which are designed to make the required powercorrection in the eye. Again, the cornea is not shown but the lenticuleoutline is shown 1410 along with the side cut 1420. In this example, thecorrection is low but the two concave surfaces have been spaced fartherapart 1430 than in FIG. 13. In addition, in order to keep the diameterof the lenticular tissue at a certain diameter, there is a transitionincision 1430 forming a transition ring around the circumference of thelenticular tissue 1430. The result is a thicker lenticular tissue withthe same correction, same diameter but easier to extract.

It should be noted that the methods disclosed here can be used toproduce other three dimensional surface shapes such as hyperopiccorrection. These methods can be applied to material processing for anytransparent or semi-transparent medium or tissue.

Added Shape Examples

In some examples, when a lenticule correction is calculated, theresultant material is relatively thin as compared to the cornealthickness. This may occur in low myopia or low hyperopia patients forexample where the correction is between 0.5 and 3 diopters (D). But athin lenticule may be difficult to extract from a cornea after it isincised by the laser as described above. Thin lenticules may tear, rip,come apart or otherwise fall to pieces resulting in trouble for anoperating surgeon. Another reason an added shape may need to be added toa lenticule is because a thin incision for low hyperopia and/or myopiamay be too thin for a femtosecond laser as described herein. In using afemtosecond laser, the cutting limit for a low hyperopia and/or myopialenticule may be below the threshold that the waist of the femtosecondlaser beam may incise.

Therefore, there is a need to add a thickness to the calculated thinlenticule in order to facilitate extraction. Referring again to FIG. 12,such an added shape would cause the calculations of the curvature cuts1230 to be spaced further apart, causing a specifically calculated spacebetween the bottom surface cut 1250 and the top surface cut 1260.

But such an added thickness should not substantially change thecalculated corrective lenticule shape calculated to correct thehyperopia and/or myopia. In other words, the added shape should havesubstantially no power of correction. Additionally, such a calculationis complicated by the procedure which may use a physical docking patientinterface for the laser system. Such a physical patient interface maydeform the eye when docked or applanated. And adding a layer of uniformthickness to the calculated lenticule under applanation will introduce arefractive error that can be a significant part of the low targetcorrection, for example 0.5D of 2Ds correction. Thus, the shape of theadded material must be customized for the correction.

FIG. 15 shows an example of these complications. First, FIG. 15 shows apatient interface 1502 docked on a cornea 1504. An example lenticule isshown 1506 cut in the cornea 1504. Also shown is the cornea 1508 in anatural, undocked position. It is clear that when the cornea returns toits natural position 1508, the lenticule 1510 has a different shape thanit did when it was incised 1506.

Next, FIG. 15 also shows the end result of the procedure 1512 where theresultant corneal curvature is reduced from Rc 1514 to (Rc−δ) and thefocal distance is reduced by δ 1516. This can also induce a myopicerror, and may be factored into the lenticule calculations.

Therefore, the size and shape of the non-corrective added shape to thecorrective top and bottom lenticular incisions, must be determined andincised so that when the cornea is allowed to assume its natural shape,the added shape adds no corrective power to the corrective lenticule.Embodiments here may be used to calculate and incise such a shape to addto a corrective top and bottom lenticule calculations. This added shapemay be the same for hyperopic and myopic patients.

FIG. 16 shows a diagram of how such an added thickness may becalculated. In the diagram, the target focal plane 1602 is shown. Thedefocus after the fixed thickness is removed 1604 is also shown. Thedistance between these points is an error ϵ 1606. The focal length fo1608 after removing a fixed thickness 1609 is shown along with the focallength fe 1610 of the target focal plane 1602 after removing the fixedthickness Δ2 1618. As is the focal length fc 1612 of the correctedcurvature after removing the first lenticule Rc 1614. The distance thefocal length was reduced δ 1616 is shown. The lenticule thickness Δ21618 is shown. The new lenticule curvature Re to correct the addedthickness 1620 is shown, where the total added thickness Δa=δ+Δ2.Further, where n_(c) is the index of medium, which is the cornea in thiscase.

$f = \frac{R \cdot n_{c}}{n_{c} - 1}$ R₀ = R_(c) − δ$f_{0} = \frac{( {R_{c} - \delta} ) \cdot n_{c}}{n_{c} - 1}$f_(e) = f_(c) − (δ + Δ₂)$ɛ = {{f_{c} - \delta - f_{0}} = \frac{\delta}{n_{c} - 1}}$$R_{e} = {R_{c} - {\frac{( {n_{c} - 1} )}{n_{c}} \cdot ( {\delta + \Delta_{2}} )}}$

Where f is focal length. Where fc is original connected focal length.Where R is radius of curvature. Where Ro is new surface if you justremove δ. Where Rc is radius of curvature if primary correction butcannot be removed. Where 6 is additional thickness that will induceerror. The total added thickness Δa=δ+Δ2 consists of two parts, auniform thickness part δ and a lenticule part with thickness Δ2. Thus,using these calculations, the added thickness Δa can be calculated toincrease the size of the lenticule, while not changing the correctivepower of it, even accounting for the applanated cornea during procedure.

CONCLUSION

All patents and patent applications cited herein are hereby incorporatedby reference in their entirety.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing some embodiments (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (e.g., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or examplelanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate some embodiments and does not pose a limitation on the scopeof some embodiments unless otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementas essential to the practice of the embodiments.

While certain illustrated embodiments of this disclosure have been shownand described in an exemplary form with a certain degree ofparticularity, those skilled in the art will understand that theembodiments are provided by way of example only, and that variousvariations can be made without departing from the spirit or scope of theembodiments. Thus, it is intended that this disclosure cover allmodifications, alternative constructions, changes, substitutions,variations, as well as the combinations and arrangements of parts,structures, and steps that come within the spirit and scope of theembodiments as generally expressed by the following claims and theirequivalents.

What is claimed is:
 1. A method for creating lenticular incisions tocorrect low myopic/hyperopic patients using an ophthalmic surgical lasersystem, the method comprising: placing a patient interface device incontact with a cornea of a patient's eye to applanate the cornea;generating a pulsed femtosecond laser beam; delivering the pulsedfemtosecond laser beam into a stroma of the cornea; deflecting, by anXY-scan device, the pulsed laser beam; modifying, by a Z-scan device, adepth of a focus of the pulsed laser beam; and calculating, by acontroller, an initial top lenticular shape, an initial bottomlenticular shape, wherein the initial top lenticular shape and theinitial bottom lenticular shape define an initial space between them,and a shape of an added space, wherein the initial top lenticular shapeand the initial bottom lenticular shape are calculated based on apredetermined correction power, wherein the shape of the added space hasa uniform thickness part with a uniform first thickness and a lenticularpart with a second thickness at its center, wherein the second thicknessis calculated based on a shape difference between the applanated corneaand the cornea in an unapplanated state, and wherein the shape of theadded space introduces zero correction power in the cornea in theunapplanated state; calculating, by the controller, a top lenticularincision shape based on the initial top lenticular shape and the shapeof the added space, and a bottom lenticular incision shape based on theinitial bottom lenticular shape and the shape of the added space;controlling, by a controller, the XY-scan device and the Z-scan deviceto form an incised lenticule in the cornea, by incising, while thecornea is applanated by the patient interface device: a top lenticularincision in the stroma of the cornea, having the calculated toplenticular incision shape and a circumferential periphery; a bottomlenticular incision in the stroma of the cornea, symmetric to the toplenticular incision, having the calculated bottom lenticular incisionshape and a circumferential periphery; and a transition ring or side cutincision intersecting the circumferential periphery of the toplenticular incision and the circumferential periphery of the bottomlenticular incision; and removing the patient interface device from thecornea.
 2. The method of claim 1 wherein the shape of the added space iscalculated based on the predetermined correction power.
 3. The method ofclaim 1 wherein the incised lenticule is at least 40 μm thick at itscenter.
 4. The method of claim 3 wherein low hyperopic/myopic patientsare 0.5 diopters to 3.0 diopters.
 5. The method of claim 1 wherein thetransition ring incision has a top edge and a bottom edge, and the topedge and the bottom edge have the same circumference.
 6. The method ofclaim 5 wherein the transition ring has a middle edge between the topedge and bottom edge and the middle edge has a larger circumference thenthe top edge circumference and the bottom edge circumference.
 7. Themethod of claim 5 wherein the transition ring has a middle edge betweenthe top edge and bottom edge and the middle edge has a samecircumference as the top edge circumference and the bottom edgecircumference.
 8. The method of claim 1 wherein the transition ring hasa diameter of between 5 and 9 mm.
 9. The method of claim 1 wherein thetransition ring is 8 mm in diameter.
 10. An ophthalmic surgical lasersystem to correct low hyperopia and/or myopia, comprising: a laserdelivery system for delivering a femtosecond laser beam into a cornea ofan eye; an XY-scan device to deflect the laser beam laterally; a Z-scandevice to modify a depth of a focus of the laser beam; and a controllerconfigured to calculate an initial top lenticular shape, an initialbottom lenticular shape, wherein the initial top lenticular shape andthe initial bottom lenticular shape define an initial space betweenthem, and a shape of an added space, wherein the initial top lenticularshape and the initial bottom lenticular shape are calculated based on apredetermined correction power, wherein the shape of the added space hasa uniform thickness part with a uniform first thickness and a lenticularpart with a second thickness at its center, wherein the second thicknessis calculated based on a shape difference between the cornea in anapplanated state and the cornea in an unapplanated state, and whereinthe shape of the added space introduces zero correction power in thecornea in the unapplanated state, and to further calculate a toplenticular incision shape based on the initial top lenticular shape andthe shape of the added space, and a bottom lenticular incision shapebased on the initial bottom lenticular shape and the shape of the addedspace; wherein the controller is further configured to control theXY-scan device and the Z-scan device to form an incised lenticule in acorneal stroma with the laser beam including incising, while the corneais applanated by a patient interface device: a top lenticular incisionhaving the calculated top lenticular incision shape and a circumference;a bottom lenticular incision symmetric to the top lenticular incisionhaving the calculated bottom lenticular incision shape and acircumference; and a transition ring incision intersecting both the toplenticular incision circumference and the bottom lenticular incisioncircumference.
 11. The system of claim 10 wherein the shape of the addedspace is calculated based on the predetermined correction power.
 12. Thesystem of claim 10 wherein a distance between the top lenticularincision and the bottom lenticular incision, as measured from theircenters, is at least 40 μm.
 13. The system of claim 10 wherein thetransition ring has a top circumference edge and a bottom circumferenceedge, and the top circumference edge and the bottom circumference edgehave the same circumference.
 14. The system of claim 13 wherein thetransition ring has a middle circumference edge between the topcircumference edge and bottom circumference edge and the middlecircumference edge is larger than the top circumference edge and thebottom circumference edge.
 15. The system of claim 13 wherein thetransition ring has a middle circumference edge between the topcircumference edge and bottom circumference edge and the middlecircumference edge is the same as the top circumference edge and thebottom circumference edge.
 16. The system of claim 10 wherein thetransition ring has a diameter of between 5 and 9 mm.
 17. The system ofclaim 10 wherein the transition ring is 8 mm in diameter.